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.312 bullets in .308 bores

I just bought five boxes of the discounted Hornady ".303 bullets" (actually .312 diameter) from Graf on sale.

I intend loading them medium hot for some of my more worn regular Mosins and snipers showing .310 -.311 in the bore, but wonder if there is any pressure danger in accidently or intentionally shooting them in tighter Mosins in the .308 range.

Can I safely shoot the larger bullets in all Mosins or do I need to carefully segregate them only to larger bores for safety reasons?

may i suggest you call sierra and ask thier opinion...
i know they clearly stated the reverse was fine and accuracy did not suffer....
so maybe they tried the other way around
and to start a small war;;;try slugging you guns again

the smallest i have seen in 10 plus years is my 28/30 at 309plus.....
i have never seen a 308 mn..never a russian...never a finn..but i never owned a 27 nor a 76...
i do know how to use a mic and i do know how to slug bores....

wouldn't do that, i noticed differences in pressure (flatter primer) in an m39 that has a .3105 bore when switching from .311 smk to .312 graf.

Just had similiar results in a PU sniper, pressure signs with .312 and none with .3105 Hornady and no degradation of accuracy. Primers may not be conclusive but they are a darn good "Indicator" to stop and adjust what one is doing.

You are right that I don't have .308 bores in anything -I need to go back to reslug some of the tight ones I have been shooting .308 in. No problem in suggesting that as things aren't too scientific if I don't measure right.

I'll try the .312 Graf in the loosest bores with a light load, perhaps a Trail Boss one first, and then work up if it goes well. That stuff seems to be good for rifles as well as cowboy action shooting.

(I just loaded 100 325 grain bullet Trail Boss light loads for my new 500 S&W revolver so a few curious souls can try it without whacking themselves in the face. Talk about a gun that attracts attention at the range! The Performance Center model with 10 1/2 inch barrel with recoil reducer and Leupold scope, in case any elephants cross the yard...my normally patient wife demanded a large offsetting cash reward to get me out of the doghouse on that purchase.)

Bullets

One PU sniper slugs to .313 and shoots .312 bullets deadly accurate with no pressure signs on primers

Other PU sniper slugs to .312 and shoots .312 bullets with pressure signs on primers but with .3105 bullets and no pressure signs. This rifle shoots .312 and .3105 bullets same superb accuracy. This rifle will be fed .3105 bullets .

Charge wt. of Varget was my match loading for above observations. Each rifle is telling me what it wants and my hopes of making .312 Hornady BTHP my one and only bullet for PU snipers and Lee Enfields is shot out of the saddle. I will have to buy and stock both .312 and .3105 bullets . Just got to juggle the logistics to keep those bullets on the shelf.

All of my Winchester 180 gr round nose mic'd out .312. 7 and 14 Russian Sniper rounds mic out @ .311. 7.62mm seems to be an about.
All of my milsurp mic's to .308 .309. my mic is good to + - 9/10ths Interesting thing 303 Brits. can mic out out 312. I seems like you could be talking type of powder slow burn fast burn and the type of primer? I don't reload, just a guess.
I shot the Winchester.312 outta the box in my PU and the groups were fine, fist size with my 43, but I can hit POA yet.@ 100m had no problems with groups. The only time I had a problem with 180 gr was in my PSL (YEAH YEAH )Winchester powder really stinks and sticks too you. I've used it in all my Mosin M39 to a Dragoon, the pin was always the problem. But I was using factory load Winchester cause that's what I could get. I had to back the firing pin out 1 full turn though which stopped the 'almost ' punching thru. I have never slugged my bores on the PUs but the rifling in all of them looks brand new.

Mantis' measurement of Winchester 180 grain round nose at .312 really has me thinking about what normal is these days -now I have to start measuring all kinds of other ammo I have around!
I just bought a ton of Graf/Hornady .312 bullets (sold for .303 rifles, but marked as .312, which is standard for .303s) intending it just for my more worn bores but if Winchester is shooting .312 in all their 7.62X54 I am surprised. Time to get the mic out...